$aml.js

var $aml = (function() {
  var me = {
    ajax: AJAX()
  };

  function formURLEncode(args) {
    var keyVals = [];
    for (var key in args) {
      if (args.hasOwnProperty(key)) {
        keyVals.push(encodeURIComponent(key) + '=' + encodeURIComponent(args[key]));
      }
    }
    return keyVals.join('&');
  }

  function AJAX() {
    var me = {
      method: 'GET',
      url: null,
      params: null,
      data: null
    };
    var exported = {
      method: setMethod,
      url: setURL,
      params: setParams,
      data: setData,
      exec: exec
    };
    
    function setMethod(method) {
      me.method = method;
      return exported;
    }

    function setURL(url) {
      me.url = url;
      return exported;
    }

    function setParams(params) {
      me.params = params;
      return exported;
    }

    function setData(data) {
      me.data = data;
      return exported;
    }

    function exec() {
      return new Promise(function(resolve, reject) {
        var xhr = new XMLHttpRequest();

        xhr.onload = function() {
          if (xhr.status >= 200 && xhr.status <= 299) {
            resolve(xhr.response);
          } else {
            reject(xhr.statusText);
          }
        };

        xhr.onerror = function() {
          reject(xhr.statusText);
        };

        var uri = me.url;
        if (me.params) {
          var encoded = formURLEncode(me.params);
          var sep = '?';
          if (uri.indexOf('?') >= 0) {
            sep = '&';
          }
          uri += (sep + encoded);
        }
        xhr.open(me.method, uri);
        xhr.send(me.data);
      });
    }

    return exported;
  }

  return me;
})();